1. Field of the Invention
This invention relates to new liquid crystal compounds having a low viscosity and being capable of improving sharpness as liquid crystal, and also liquid crystal compositions containing the same.
2. Description of the Prior Art
Liquid crystal display elements utilizing the optical anisotropy and dielectric anisotropy of liquid crystal substances are classified into various modes such as TN type (twisted nematic type), DS type (dynamic scattering type), guest-host type, DAP type, etc., depending on their display modes, and the properties of liquid crystal substances suitable to the respective uses vary. However, it is common to any of these liquid crystal substances that they are required to be stable to moisture, air, heat, light, etc. Further, it is desired that they exhibit a liquid crystal phase within a temperature range as broad as possible, around room temperature, and have a viscosity which is low enough not to reduce the response rate of display elements even at low temperature, and further have an optimal value of dielectric anisotropy (.DELTA..epsilon.) which varies depending on the kinds of display elements. However, substances which satisfy such conditions by their single use have not yet been found, and it is the present status that liquid crystal compositions obtained by blending some kinds of liquid crystal compounds or non-liquid crystal compounds have been used. In particular, the need for multiplex display to be used in liquid crystal display apparatus has recently been increasing, and it has been desired that as to such liquid crystals to be used for the multiplex display, the so-called .gamma. value (Vsat (saturation voltage)/Vth (threshold voltage)) indicating their sharpness be small.